Fractional crystallization



July 15, 1952 H. J. PANKRATZ ETAL FRACTIONAL CRYSTALLIZATION 3 Sheets-Sheet 1 Filed Jan. 26, 1950 INVENTORS. H.J. PANKRATZ 1 H. A. DUTCHER y c. E. ALLEMAN FIG. 6.

ATTO NEVS y 15, 1952 H. J. PANKRATZ EI'AL 2,603,667

FRACTIONAL CRYSTALLIZATION Filed Jan. 26. 1950 3 Sheets-Sheet 2 SOURCE ATTORNEYS July 15, I952 ,l-l. J. PANKRATZ ETAL FRACTIONAL CRYSTALLIZATION 3 Sheets-Sheet 5 Filed Jan. 26, 1950 INVENTORS. H J. PANKRATZ H. A. DUTCHER C. E. ALLEMAN A T TOR/YEKS Patented July 15, 1952 FRACTIONAL ORYSTALLIZATION Howard J. Pankratz and Harris A. Dutcher, Bartlesville, Okla, and Carl E. Alleman, Cactus, Tex., assignors to Phillips Petroleum Company, I I

, a corporation of Delaware Application January 26, 1950, Serial No. 140,644 13 Claims. (01. 260707) This invention relates to a continuous fractional crystallizer. In one of its more specific aspects it relates to an improved fractional crystallizer of the continuous crystal conveyor type for the separation of mixtures. In another specific aspect it relates to the purification of compounds by crystallization. In another specific aspect it relates to an apparatus for carrying out fractional crystallization. r

Fractional crystallization is a process for separating one component of a mixture from the remaining component or components by causing it to crystallize out and removing the crystals from the zone of crystallization to a melting zone from which the component is'recovered as a melt. In most cases the crystals which are formed are of the higher melting component of the mixture; however, in the case of eutectic mixtures the crystal may or may not be of the higher melting component, but will be of that component present in excess of the eutectic ratio. Apparatus previously developed for the separation of crystals from mother liquor in the process of fractional crystallization have generally been of the reciprocating type, i. e. comprising an elongated cylinder with a conveyor therein which when moving in one direction moves crystals from the crystallizing end of the apparatus to a crystal removal zone and when moving in the opposite direction to pick up another group of crystals passes through the materials being separated with as little'disturbance as possible. The obvious disadvantage of suchan apparatus is the turbulence caused in the materials being separated by the movement of the conveyor when going back to pick up more crystals. Such turbulence greatly cuts down the efficiency of the apparatus. This problem is one of those avoided by applicants with the development of their apparatus. Another problem also encountered in such apparatus isjamming of the conveyor when large quantities of crystals are formed. This also has been overcome in the apparatus of applicants.

An object of this invention is to provide an improved process and apparatus for continuous fractional crystallization.

Another object of this invention is to provide an improved apparatus for the separation of mixtures by fractional crystallization. 7

Another obj ect is to provide a fractional crystallization apparatus wherein the crystals are washed advantageously thereby enabling the recovery of more pure compounds; I

Still another object of this invention is to provide an improved fractional crystallization apmatically.

2 paratus and a method for operating same auto- Further. objects and advantages of this invention will be apparent to one skilled in the art from the accompanying disclosure and discussion.

Refer now to the drawings. Figure 1 is an elevation view of one modification of our invention wherein a liquid seal is used between the separated components. 1

Figure 2 is a diagrammatic view of the mecha- I nism used in conjunction with the apparatu of Figure 1 for simultaneously opening the solenoid valves in the feed inlet and in the product withdrawal lines and cutting off the power'when'the piston has'completed its stroke.

Figures 3 and .5 are schematic diagrams oithe controlling apparatus used in conjunction with the crystallizers of our invention;

Figure 4 is an elevation view of a preferred embodiment-of our invention including apparatus for intermittently washing the crystals; formed with purified product; I 1

Figure 6 is a vertical cross section of asurge chamber used in conjunction with-apparatus of Figure 4.

Figure 7 is an elevation view of another embodiment of our invention utilizing gas or vapor to separate the purified components of the mixture being eparated.

Figure 8 is a cross sectional view of one, type of apparatus for driving the continuous conveyor used in the apparatus of our invention.

Figure 9 is an isometric view of a suitable conveyor flight which is used in the apparatus of our vention.

' Figure 10 is a front elevation of one embodiment of the sprocket'used for driving the continuous conveyor, and shows the relationship between the sprocket and conveyor.

Refer now to Figure 1. Number 'I 5 is a'v'erticall'y positioned housing for a continuous conveyor, preferably of a circular cross section and having an over-all shape of a loop'with a U'pocket. LNumher It is the housing containing the drive mechanism for the conveyor. Thi unit-more fully-discussed with respect to Figure 8; contains a heavy sealing liquid, heavier than theliquid in housing I5. This liquid is any which is heavier than the liquid inthe housing and-which is immiscible and unreactive with thecontents of housing 15. Mercury is particularly advantageous, howeverothers such as glycerin, water, glycols, and the like'niay be selected depending on the particular materialsv being separated. Any mixture which can beseparated by fractional crystallization canbe separated by the practice of our invention. Examples of such mixtures include, a mixture of benzene and n-heptane, a mixture of p-xylene and m l xylene, a mixture of o-cymene and'm-cymene, and

the like.

Any suitable continuous flexible conveyor with perforate flights may be used, either of the link connected or cable type, such as for example that shown in the cut-away portion la of housing l5. Number I! is a cylinder mounted above housing '16 containing a piston for applying pressure on the liquid seal and therefrom to the materials being separated, and in this manner j improving the separation. A suitable means for V 7 moving the piston in cylinder I"! is motor it which furnishe 'powerthrough gears l9 and 2: to'crank 22 and therefrom to connecting rod 2 3 and vertical the lug i on the upward stroke. When the lug it engages the arm of the switch 42 on the upward movement. of the shaft 24, contacts of the circuit comprising lines 50 and 50b are closed momentarishaft 24. Coil 26 around housing [5 is for apply- I ing heat to cause the-melting of crystals so that the material from which .they are formed may be withdrawn as a liquid. The temperature prevailing in coil 26 can vary overa wide range, and the temperature in any particular case is known-to. 7 those skilled in the art since it must be at least high enough to melt the crystals as'hereinbefore' describedand the melting point. of any particular component is known-to the art. The heating coil. is diagrammatic and includes other heating means such as electrical heaters (induction) and the like. Coil 21, opp site coil 26 is for cooling the r liquid in housing [5 to cause the separation of one 4 of the components therein' ascrystals which are carried away by'the conveyor which is traveling continuously regardless ofthe pressure cycles to which it is being subjectedin the direction of the arrows 28. Thetem'pe'rature prevailing in coil 21 can also vary over a wide range, the temperature in any particular'case being sufficientlylow to cause separation of one of the components of the mixture from the mixture byfreezing that componentiout, as crystals. The temperature in any particular case necessary for this separation is also known. to the art and therefore will notbe from the drive unit 16. Sealing liquid can extend into housing I 5 from drive unit It any desired distance so long asmovement of the sealing liquid] hereinafter described does not result in loss of the liquid through either of the lines38 or 39 and so long as the purified component below heating coil 26 cannot communicate with the liquid component contained-in housing lfi below cooling coil 27. Line 3| is an inlet to housing I5 for a mixture of f materials to be separated by'the process of frac- 1 tional crystallization. Solenoid valve P1 in line 3| is supplied to enable shutting off the feed to housing l5 when pressure is applied on the sealing r liquid. Check 'valve 32 is placed in line 3| to pre- 3 vent back flow of liquid and pressure on valve P1. 1 Lines 33 and '34 containing valves 36 and 31 re-' spectively are provided to enable filling housing l5 liquid full. These valves, once the apparatus has been charged with liquid, are in a normally closed further discussed. Number 29 indicates the level Q "of the sealing liquid extending into housing i5 ly, thereby actuating-the solenoid of contact 5! (seeFiguIe 3). Sufficient inertia is present in the power means to carry the vertical shaft 24 upward sufficiently far to cause disengagement of lug with switch 52 allowing spring 44 to move the tact is broken.

Refer now to Figure 3 which shows the relationship of the'switch mechanism of Figure 2 with the crystallization apparatus. of Figure 1, causing a .switch,;,to a position suchthatthe electrical c011 continuous and controlled operation thereof.

Similar apparatus-to 'that'in Figure l'will be similarly numbered. The apparatus discussed in relation with this drawing. is: that which causes regular intermittent application of pressure on the liquid within'the crystallizer and concomitant closure of thevalves P1-Fs. Number it is a cam V of a conventional timer rotated by a suitable motor and which on rotation intermittently closes plunger-contact '41 which is normally spring biased open. on closing'the circuit 52 and 52a, which leads from a power supply,power is passed to circuit 53 and 53a, which leadsto motor 58, thus causing it to become energized. The lug il at tached to the vertical shaft 24 and the switch 52,

discussed in regard to Figure 2 and represented byfbox 68, are so positioned that the switch is actuated by the lug only when piston 49 in cylinder l1 nears the top of its stroke. When the circuit comprising lines52j and 52a is completed by raising contact 41 thejsolenoids of normally biased open valves Fi -P3, which are those indicated in Figure l, are energized causingthe valves to close at thesametime. thatmotor H? Y starts. When cog 2i has almost completed a full position. Line 40 and valve 55 are provided for trapping and, removing or any of the immiscible sealing liquid that is carried from the U pocket into the loop of the housing in crevices of the conpl ed on. the. eal liquid. and. concomitantlyon Qthe liquid being separated in the crystallizer. Line 39 leading from housinglE below coil 27 is I 31150 qr oving s parated. material and, is. c1 75 revolution thus lowering and raising the piston 39 once the switch 42 of Figure 2 represented bybox A8 is actuated and likewise the circuit comprising lines 50, 56a, and b causing the solenoid actuated contactil, normally in a closed position,

to be opened thus'breaking the circuit to motor l8 and causing piston 49fto besstopped in a raised position. The opening of contact 5| also de-energizes the solenoids of valves P1P3, thereby allowing the valve to open. Contact 5i'i normally closed by gravity, however, if it were allowed to close immediately after it has opened, it

is conceivable that it might close before cam 35 has moved a sufficient distance-to allow contact 4'! to break the circuit 52 and 52a, therebystarting up motor I8 before desired. To avoid such an occurrence, dash pot is connectedto the movable core of the solenoid attached to contact 5! and so adjustedas to provide suitable lag in the closing of the contact 5]. co-allow contact lz'i to open so the circuit comprising lines 52 andEZa will remain open until it is necessary to repeat the pressurecycle. Conventional solenoid valves,

This spring moves switches, contacts, and the like such a are well known to those skilled in .the artgcan be used. 7

Refer now to Figure fl which' 151013, preferred embodiment ofiour invention. In j-this einbodiment the pressure applying apparatus of Figure l is used to provide an intermittent backwash of the formed crystals in the crystallizer. "The crystallizer shape is also the same, as are the valves P1-P3. For this reason similar pieces of app-aratus will be similarly numbered. The specific dif ference in this apparatus over that of Figure 1 is the means for withdrawal of products and the flushing of the crystals with product obtained by melting the crystals. In the operation of this apparatus the electrical circuit-s shown in Figure 3 and previously discussed are 'used with the exception of box 48 which is supplanted by the box 58 of Figure 4 containing the two over-center switches of Figure 5. In addition, the circuits of Figure5are also'used. 1 q I As in all of the embodiments disclosed, the crystal conveying apparatus and the power source operate continuously irrespective of whether the flushing action, hereinafter described, is taking place. In the operation of the apparatus, product comprising the melt from the crystals is withdrawn through line 38a and solenoid valve P: and is passed to storage tank 56. Similarly, liquid is withdrawn via line 39a, check valve 54, and solenoid valve P3 and is passed to storage tank 51. These are the means used for handling the liquid products when in normal operation without any pressure applied. When pressure is being applied by piston 49 the valves P1-P3 are closed, three-way valve P5 is positioned so that surge chamber 6| communicates with housing l5, and three way valve P4 is positioned so that surge chamber 61 communicates with is more clearly shownin Figures 3 and 5. Refer now to these figures along with Figure 4. When motor [8 is stopped, the vertical shaft 24 is at its uppermost position, and the lug 4| is above the arm of over-center switch 1|, also in an upward position. In this position of switch 1| circuit 5858b supplying power to the solenoid operating contact 5| is open, thereby allowing this contact to remain closed. Similarl'y'the circuit comprising line 66, more completely described below. The

stroke of piston 49 isso adjusted as to displace only the amount of liquid which surge chamber 6| will receive. This chamber may be designed for-any desired volume, the volume equalling. that which is to be flushed throughthe crystals on' theopposite side of the crystallizer. In this manner all the liquid displaced in housing l5 passes into chamber 6| causing washing action on the crystals above heating coil 26 by the flow of liquid toward the outlet comprising line 39a. I Upon piston 49 reaching the bottom of its stroke valve P5 is reversed in such a manner that surge chamber-6| is shut off from line 59, but is opened to line 62, thereby allowing it to drain into tank 51 through line 39a. While valve P5.

is allowing liquid to be passed into surge 'cham- I ber 6l, valve P4 is so positioned as to allow pump 63 to withdraw a portion of the liquid from storage tank 56 via line 64 and pass it through line 66 into surge chamber 61. This valve is also a three-way valve whichwhen open tothe surge chamber'61 and line 66 is closed to line 68. Line 68 contains a check valve 69 to prevent back flow of product from housing 5 into the surge chamher. When pressure is being released on the liquid in the crystallizer, valve P4 is reversed, open-. ing the surge chamber 61 to lin'es 68'and'38a and allowing the liquid therein to flow into the crystallizer replacing that which was withdrawn'under pressure and causing additional washing of the crystals. Valves P4 and P5 are normally biased to the position shown in Figure 4.' Eneirgization of their solenoids reverses their posi- The mechanism for operating the valves of the embodiment of our invention shown in Figure 4 lines 86, 18, 19, 8|, 82, 83, and 84 to valve Pris open allowing the'valve to remain inits normally spring biased position, which provides passage from line 68 to surge chamber 61. While overcenter switch 1| is in its upward position, overcenter switch 12 is in a downward position which maintains the circuit comprising-lines 86, 81, 88, and 82 open andthereby the valve P5 in its normally spring biased position which provides a passage from surge chamber 6| to line 62. With switch 1| inits' upward position the movable core of solenoid 13 is in an upward position also. With the core extended in this manner, held by over-center spring 14, the contact 18 thereon is open, thus maintaining the circuit 86, 89, 9|, 92, and 82 inactive. Withs'witch 12 in a downward position the core of solenoid 16 is also in a downward position and'the contact 15 is' closed, howeverjthe circuit comprising lines 86, 18, 19, 8|, 82, 83, and 84 still }remains inactive, since the circuit is broken at switch 1|. The over-center spring 11 holds the core 'of solenoid 16 in its downward position. p g j v As the lug 4| on shaft 24 moves downward, it pushes the arm of switch 1 downward until the spring -thereon moves it to itslowest position.

-When this happens, circuit comprising lines 18,

19, 8|, 82, 83, 84, and 86 is closedandthe solenoid of valve P4 is activated, causing the valve to providea'passage from line. 66 to surge chamber 61. At the same time the circu it 86, 18, ,19, 8|, 84, 83, and 82 is activated, causing the, solenoid 16 to become activated and the corethereof to push the arm of switch 12 upward. This closes the circuit comprising lines ,86, 81, 88, and 82, thereby activating .valve P5 and putting'it in a position to make a passage way from line 59 to surge chamber 6|. As switch 1| is pushed in a downward position, the corejof solenoid 13 is also pushed downward. However, dash-pot 93 is attached thereto to slowdown the movement of the core downward to'the speedat which shaft 24 is moving. In this way switch 12 is activated before the contact 18 on'the core of solenoid 13 connects lines 89 and 9|. This prevents completing of the circuit comprising lines 86, 89, 9|,

lug 4| contacts the arm 'ofswitch 12, pushing it.

downward until the switch takesit original downward' position. In this manner' the circuit86, 81, 88, and 82 isbroken allowing yalve P5 .to take its original spring biased position. -When'switch12 takes this'downward position the circuit 86, 89,

9|, 92, and 82 is closed, thus activatingthe solenoid 13 and causing the 31 core thereof to push switch 1| in its original upward position. In this position of switch 1| the circuit 88, 18, 19, 8|, 84, 83, and 82 is broken allowing valve P4 to assume its original spring biased: positions.

In'order toprolon'g' the life of thesolenoids 13 andiia provisionismacle tor immediately-die connectingt "soleno dkaiter: tihas been ach ezlz1respectively wil during-portionsof the stroke; D sh po nd flarprovide theine e saryireta rded mov ment ;for'

w, efioontaets 7:195 hmantains o-the circuit sequence operation-and springs, 141 and J1 the 1 V necessary force to complete the movement" of the v solenoids iaiand'rlfi respectively after'thecircuit has'beeii'sbroke'n. 3 However; in the; instancesofj switch :12, itiis;necessarytoamaintain a 'connection between'lines '18 and 8| afterrcontact-lfihas. been brokenfifI-l'iis i'sdonehyrusing contact 8 0 and the byi-pass circuit comprising lines. $34,188; and :9! andiresistance' T98: Contact- W? is. so positioned to provide a constant supply Oipower'to valve P4 while; the: core 'fOfi solenoid: "1 6, changing the contactsin the "circuit "from 15,120 '30. I The :re-

si'stance '98 is equal; to the resistanceiprovided by solenoid; 15.: 7 Spring [4 and H maintainsjthe solenoid 113; or; 16. :in either an upward or down wardpositiom 1;; 11 :1 1 a 'Nearrtheftop of; the upward stroke of shaft 24 a while coil I24 is the cooling coil traveling. With it moving in the direction indicated coil I23 is a heating coil for melting crystals of the material to be withdrawn-through line, I I8,

Refer now to Figure a hich is} of one ihbodi merit of the drive means for theembodiments of my crystallizer shown in Figures 1, 4,.- and '7.

This apparatus must be modified somewhatto be used in the apparatus of Figure 7,by,passing the conveyor over the sprocket drive. wheel rather than under, and removal or non-use of themessure applying piston. In the drawing number I26 is the base for motor 121i and the housing I28. Number I29 is the power transmitting shaft from motor IZ'I to sprocket I3 I. Thisshaft is supported 7 inside of housing IZBby bearing I32. Stufiing box I33 is present to prevent the leakage of the heavy sealing liquid which is present inside of housing I28. Number I 35 is the ,vertical cylindrical housing as shown in Figures 1 and 4. Number I36 is a top closure memberfor. this cylinder through which vertical shaft 2 5 pas ses,wh ich is the lug. thereonqcontacts the arm of switch II pushing it. still further upward and against spring 93 until it has passed'over-the end of the arm.

By -s0 operating :tbeeircuit 5fl 5ilb i closed for a V brieofjiinstant', thereby :supplying power to the s eno dnicon et t-pr ab nsth c r it; h motonIB, causing itto stop at the topof its stroke. As previously discussed, the dash-pot -55 is at tached to the solenoid of contact-5i to delaythe closing of this contact untilthe circuit comprising lines 5 2 and 52 ,a has been broken by the timer.

Refer .now .to Figjure 6, which is of oneembodiment ofthe surge chambers GI and 67 and valves} attached thereto used with thegapparatus' of Figure. Other conventional apparatus of, this type maybeused. -Number ,Iill viswa cylindrical housing, 'partially closed at one. end, of suitable diameter and'len'gthgto hold,the desired volume ofliquim Number [8-2 'is jabottom closure mem ber forsaid cylinder sode igned that t may t readily attached to said cylinder and to i three-u way, valve I33. Number I014 is a piston having axial guide "it around whichi spring motor I0! is positioned. Number IDB'isanadjustabIy positioned bushing; around guide I 05 and in the end of cylinder :IflIQfor varying the tensionon spring motor IQ'L Other suitablemotor means may be used'as will be' well known to those skilled-in the art. 'Numbers I539 and III are conduits attached,

to valve I 03 through which" liquid is 'passed.

Number I I2 is the arm attached to core H3 of the valve to'which is attached a suitable means formoving same, such'as aso'leno'id; V i v a 7.: Refer now to Figur 'i, which is of still another V embodiment of our-invention; shown in this -diagram' is scmwhatsimilar to that shown in Figu'rel; This apparatus in operation futilizes a gas or vapor phase at the top of the,

The apparatus oval housing'for maintaining the products separate; The construction of the crystallizer housing I r 1 H6 .ispreferably circular in cross-section and ovalinitsgeneral configuration. Line II! is the attached topiston 49, asshown in Figures 1 and 4.

Numbers 31-are conveyor fli hts shown in relationto sprocket I3I; -i Figure 9 is or one 'conveyor flight-showing the perforated construction of-theiilight and the r Screen bvi 11it? ;im eans su h la' .bv rivets- I M. "Thelconveyorjafiieht is attached to pinnot shown withsuit'able washersasof'neov prene rubber betweenlthe links amine, conveyor flight. Suificient space is allowed in the-flight above and below the normalposition of the links extending therethro-ugh to: allow {the conveyor to be I moved easily :through curved housings. The links- I4 2 and 1 43;;extending-;.;through the flight are attached to links I41 and 148; as by V pin-I49.

Figur-e 10 shows the method by whichuthe conveyor in the crystallizer is'moved by the sprocket Wheel I 3i of Figures. The links of the conveyor are so assembled as-to allow the o teeth: of the sprocket wheel die-extend therein feed inlet to the crystallizer and contains a valve for adjustment of flow therethroughs Lines H8 and IISare for product withdrawaland contain valves for control of'the rate ofwithdrawal. -Number"I2I indicatesthe motor and drive means for the conveyor inside housing II6 which is similar to that; shown in. subsequent Figures exceptthat there isnopiston for applying pres v sure. The arrows 'IZZ'indic'atethe direction ;in' j which :the crystal conveyor inside housing I I 5 is thus; providing for thetra'nsmission-of movenent from the sprocket to the conveyor.

The above description, of the conveyor flight, conveyorLand, power means aszshown in-Figures 81-10 is merely used as" one iexamplepf apparatus of; this type which may be;us'ed.;: Many other types 10f continuous conveyors are known, such as those using flexible cable's instead of 'links,

. and, various different types of-flights. 'Any'of theseiwhich imayibe adapted for use in apparatus ofthe type disclosed may be used, and their use isjintended to; be withiii invention; :1 3*: 2' I q t Y Although this invention has been described e 'sc'oD'e' of this and exemplified in terms ofiiit-s preferred n'io dificationsrit is understood-that 'various"changes may be made without-departing from the spirit ,with said conveyor for causing same to move in the direction from, said cooler past said inletand toward said-heatenan outlet from said conduit at the end of said cooler opposite the direction of movement of said conveyor and a second outlet at the end-of said heater in the direction of movement of said conveyor, and

' meansfor maintaining an immiscible fluid phase between said outlets for separating products of fractional crystallization.

2. An apparatus according to claim 1 wherein said hollow conduit is of circular cross-section.

3. An apparatus according to claim 1 wherein said hollow conduit is in the shape of a loop with a U pocket, said housing being positioned in said U pocket. W a

4. An apparatus according to claim 1 wherein said hollow conduit is in the shape of an oval.

5. An apparatus according to claim 1 wherein said endless conveyor is comprised of links and perforate flights pivotally attached thereto.

6. An apparatus according to claim 1 wherein said inlet is about midway between the ends of said conduit.

7. A fractional crystallization apparatus comprising a hollow conduit in the shape of a loop with a U pocket, a closed housing attached to the ends of said conduit in said U pocket for containing an immiscible liquid phase between the products of fractional crystallization for maintaining same separated, an endless flexible conveyor within said conduitand said housing, means communicating with the inside of said housing for applying intermittent pressure on liquid therein, a heating coil around said conduit, near one end thereof and a cooling coil around said conduit near the opposite end thereof, an inlet to said conduit for liquid to befractionally crystallized, means within said housing in communication with said conveyor for causing same to move in the direction from said cooling coil past said inlet and toward said heating coil, an outlet from said conduit at the end of said cooling coil opposite the direction of movement of said conveyor forproduct and an outlet from said conduit at the end of said heating coil in the direction of movement of said conveyor for product, and means for closing said inlet and "said outlets while pressure is being applied.

' 8. In an apparatus according to claim 7, means at the uppermost points of, said conduit for bleeding off gas as said crystallizer is being filled.

i 9. An apparatus according to claim '7, wherein said means communicating with the inside of said housing comprises a cylinder attached to said housing andfreely communicating with the inside of said housing, a reciprocatable piston within said cylinder, an axial shaft attached to said piston, a motor, and means'connecting said motor to said shaft for causing said piston to reciprocate when said motor is actuated.

10. A fractional crystallization apparatus comprising a vertically positioned, hollow circular conduit in the shape of a loop with a U pocket, a closed housing at the bottom of said pocket attached to the ends of said conduitallowing free communication between the ends of said conduit in said U pocket for containing an immiscible phase between the products of said-fractional crystallization for maintaining same separated,

and said housing; means freely communicating,

with the inside of said housing'for applying intermittent pressure on liquid therein comprising a vertically positioned cylinder attached to the top of said housing, areciprocatable piston within said cylinder, an axial shaft attached to said piston, a motor, means connecting said motor to said shaft for causing said shaft and said piston to reciprocate when said motor is actuated; a heating coil around said conduit near one end thereof and a cooling coil around said conduit near the opposite end thereof, an inlet to said conduit intermediate the ends thereof for liquid to be fractionally crystallized, means within said housing in communication with said conveyor for causing same to move in the direction from said cooling coil past said inlet and toward said heating coil, a product outlet from said conduit at the end of said cooling coil'opposite the direction of movement of said conveyor and a product outlet from said conduit at the end of said heating coil in the direction of movement of said conveyor, means for controlling the application of pressure and for closing said inlet and said outlets comprising normally open solenoid valves in said inlet and said outlets, an electrical'circuit connecting in parallel said valves and said'motor for actuating said piston, a timer in series with said circuit which upon reaching a predetermined position closes said. circuit thereby actuating the solenoids of said valves causing them toclose and starting said motor and causing said piston to reciprocate, a lug on said axial shaft which is attached to said piston positioned to actuate a contact in a second circuit in parallel with the first circuit when said piston is at the top of its stroke causing a solenoid contact in series with said first circuit to become actuated thereby breaking said first circuit and causing said motor to stop and said-solenoid valves to open, and a dash pot attached to' said solenoid contact for slowing the closure of said contact until said timer has reached a position at which said first circuit will remain broken. 7

l1. A fractional crystallization apparatus which comprises a vertically po'sitioned hollow circular conduit in the shape of a loop with. a U.

pocket. a closed housing at the bottom of said pocket attached to the ends of said conduit allowing free communication between the ends thereof for containing an immiscible liquid phase between the products of said fractional crystallization, an endless flexible conveyor within said conduit and said housing,.means freely communicating with the inside of said housing for applying intermittent pressure on liquid therein, a heating coil around said conduit near one end thereof and' a cooling coil around 'said' conduit near the opposite end thereof, an inlet to said conduit for liquid to be fractionally crystallized, means within said housing for moving said con veyor in the direction from said cooling coil past said inlet and toward said heating coil, an-outlet for-said conduit for product at the end of said cooling coil opposite the direction of movement of said conveyor and an outlet from said conduit 7 =ror product'at the end of said heating coil in the direction of movement of said conveyor, solenoid valves for closing said inlet and saidoutlets while pressure is being applied, afirst surge chamber connected with the outlet at the end of said cooling coil between said solenoid valve and said conduit,means forropening said first surge chamber 'to said'outlet when pressure is being applied by said piston and thereby'allowing said chamber to'fill with liquid, means for discharging, said first surge" chamber to storage when pressure is not being applied, a second surge chamber connectedwith the outlet at the end of said heating coil between said solenoid value and said conduit,

' axial shaft attached to said piston, said lug being means for closingoff'said second surge chamber when pressure'is' being applied and concomitantly fillingsaid second surge chamber from storage, and means for discharging said second surge chamber into said conduit as pressure on the liquid therein is being reduced thereby'replacing the liquid withdrawn in the first mentioned chamber.

12. A fractional crystallization apparatus comprising a vertically positioned hollow circular conduit in the shape of a'loop with a U pocket, a closed housing at the bottom of said pocket attached to the ends of said conduit allowing free communication between the ends of said conduit, an endless flexible conveyor within said conduit and said housing; means freelycommunicating with the inside 'of said housing for applying intermittent pressure on liquid therein comprising a vertically positioned cylinder attached to the top of said housing, a reciprocatable piston within said cylinder, an axial shaft attached to-said piston, a motor, means connecting said motor to said shaft for causing said shaft and said piston to reciprocate when said motor is actuated; a heating coil around said conduit near one end thereof and a cooling coil around said conduit near the opposite end thereof, an inlet to said conduit intermediate the ends thereof for-liquid to be fractionally crystallized, means within said housingin communication with said conveyor for causing same to move in the direction from said cooling coil past said inlet and toward said heating coil, a product outletfrom said conduit at the end of said cooling coil oppositethe direction of movement of said conveyor and a product. outlet from said conduit at the end of said heating coil in thedirectionrof movement-of said conveyor, afirst solenoid valve forclosing said inlet, a second solenoid valve for closing said outlet at theend of said cooling coil and a third solenoid valve for closing said outlet at the end of said heating coil while pressure is being applied, a first-surge chamber connected with. the outlet at the end of said cooling coil between said second solenoid valve and said conduit with a first three-way solenoid valve normally biased in a position allowing passage from said chamber to storage, a

second surge chamber connected with theoutlet at the end of said heating coil between said third solenoid valve and said conduit with a second three-way solenoid'valve normally biased in a position allowing passage from said chamber into said outlet; means for opening and closing said first, second, and third solenoid, valves, for actuating the motor drive for said piston, and for opening and closing the first and second threee way solenoid valves which comprises a first elecso positioned that on the downward stroke of said piston a double-pole double-throw switch is reversed thereby closing a second electrical circuit containing said'second three-way solenoid valve and thereby reversing same, a first solenoid the core of which extends outward from each end, the position of which-is concomitantly reversed with said double-pole "double-throw switch from that position caused by actuation of said first solenoid to that ready for actuation, the closing of said second electrical circuit concomitantly actuating a second solenoidso positioned that the core thereof reverses a single-pole double-throw switch which in turn closes a third electrical circuit containing said first three-way solenoid valve, a contacton the core of said first solenoid which on reversal of the core closes a fourth electrical circuit containing the coil thereabout, the reversal of said single-pole double-throw switch breaking the fourth electrical circuit containing the coil of said first'solenoid, said lug on said vertical shaft near the bottom of its downward stroke reversing the position of said single-pole double-throw switch thereby actuating the fourth electrical circuit containing the coil of said first solenoid thereby reversing said first solenoid and causing said double-pole, double-throw switch to be reversed thereby breaking said second electrical circuit containing said second three-way solenoid valve causing same to resume its normally biased position and concomitantly breaking said third electrical circuit containing said first'three-way solenoid valve allowing it to 'resume its normally biased position, said lug near the toplof the stroke of said piston contacting the arm of said double-pole double-throw switch depressing same and makin'g a brief contact thereby closing a fifth electrical circuit containing a solenoid actuated switch the contacts of which arein series with said, electrical circuit containing the motor driving said piston and actuating said solenoid actuated switch thereby breaking said first electrical circuit for a-sufiicient length of time to allow said timer to resume a position maintaining said firstelectri'cal circuit broken. a

13. A fractional crystallization process which comprises introducing a mixture-to be separated to a fractional crystallization'zone, cooling said mixture and thereby causing one component thereof to separate as crystals, continuously moving said crystals from the cooling zone to a heating zone, melting said crystals and withdrawing the melt as product of the process, recovering the non-crystallizing component as a second product, intermittently applying pressure to the mixture being separated and concomitantly stopping introduction of said mixture to be separated and Withdrawal of the melt, continuing. to withdraw non-crystallizing materialiwhile said pressure is being applied, suspending withdrawal of noncrystallizingmaterial as pressure is released andconcomitantly introducing previously withdrawn melt'to the crystallization Zone. through the'melt Withdrawal ZOfi iii 'siifiici'eht quantity to replace HOWARD J. PANICRATZ. 5 HARRIS A. BUTCHER. CARL E. ALLEMAN.

REFERENCES CITED The following references are of record in the 0 file of this patent:

Number UNITED STATES PATENTS Name Date Williams 4-. Apr. 9, 1889 Schulze Dec. 12, 1922 Baker Dec. 3, 1929 Skogmark May 10, 1932 Bottoms Feb. 21, 1933 Freeman Sept. 13, 1949 Arnold Feb. 6, 1951 Arnold Feb. 13. 1951 

1. A FRACTIONAL CRYSTALLIZER COMPRISING A HOLLOW CONDUIT, A CLOSED HOUSING JOINING THE ENDS OF SAID HOLLOW CONDUIT, AN ENDLESS FLEXIBLE CONVEYOR WITHIN SAID CONDUIT AND SAID HOUSING, A PLURALITY OF PERFORATE FLIGHTS ATTCTED TO SAID CONVEYER, A HEATER AROUND SAID CONDUIT NEAR ONE END THEREOF AND A COOLER AROUND SAID CONDUIT NEAR THE OPPOSITE END THEREOF, AN INLET TO SAID CONDUIT FOR LIQUID TO BE FRACTIONALLY CRYSTALLIZED, MEANS WITHIN SAID HOUSING IN COMMUNICATION WITH SAID CONVEYER FOR CAUSING SAME TO MOVE IN THE DIRECTION FROM SAID COOLER PAST SAID INLET AND TOWARD SAID HEATER, AN OUTLET FROM SAID CONDUIT AT THE END OF SAID COOLER OPPOSITE THE DIRECTION OF MOVEMENT OF SAID CONVEYOR AND A SECOND OUTLET AT THE END OF SAID CONVEYOR, AND DIRECTION OF MOVEMENT OF SAID CONVEYOR, AND MEANS FOR MAINTAINING AN IMMISCIBLE FLUID PHASE BETWEEN SAID OUTLETS FOR SEPARTING PRODUCTS OF FRACTIONAL CRYSTALLIZATION. 